This invention relates to a thermal analysis system for concurrent thermogravimetry and differential thermal analysis.
Thermogravimetry (hereinafter referred to as TG) is a procedure whereby a sample of a substance to be analysed is subjected to a controlled temperature program. Changes in the mass (weight) of the sample are detected and plotted against a steady temperature rise (dynamic TG) and also, if desired, against time (at constant temperature, isothermal TG).
Differential thermal analysis (hereinafter referred to as DTA), on the other hand, is essentially a qualitative method of comparing thermal changes in a sample of the substance under study with those in a sample of an inert reference substance, e.g. alumina. The two samples are subjected to the same temperature program, while the actual temperatures of the samples are measured by fine thermocouples. Differential connection of the thermocouples provides an output signal representative of any exothermic or endothermic change taking place in the active sample. This value is also plotted against temperature and, if desired, time. Another variable that can be introduced is the nature of the ambient atmosphere. For example, different plots will be obtained for DTA carried out in air or in an inert atmosphere such as argon.
Together, DTA and TG constitute a powerful combination to provide valuable information about the thermal behaviour of materials under various conditions and for the identification of substances.